 I want to take a minute just to talk about rolling element bearings. Compared with journal bearings, rolling element bearings replace the sliding lubricated friction style of interface between the journal and the bearing with rolling elements. So these rolling elements can be either balls or rollers or or pins. And the idea is that because you have these these moving mechanical parts, you can carry higher loads because you actually have a contact occurring. They have lower starting friction than journal bearings, again because of these these moving parts rather than a friction interface. And therefore they're suitable for applications with which have those high loads, high high starting loads, lower speeds, things like that. They're ill suited for high speed applications because the the thing that these moving components introduce is fatigue, right? Lots of cycles, high speeds lead to lots of cycles very quickly and the stresses then can cause fatigue failure more rapidly when you have all these moving parts compared to journal bearing. Rolling element bearings have been around forever. You know, the book talks about how the the modern version of these were developed by Da Vinci in around the year 1500. However, there's there's evidence of them existing as far back as 650 BC. However, they weren't particularly useful until more recently. Because of the high contact stresses, they require materials that are fairly hard. And steel hardening technology is a little bit more recent, the ability to do that. And that has allowed for rolling element bearings to be more successful. Within rolling element bearings, we have, as I already mentioned, a couple of different versions sticking to, you know, very high level. We'll just say ball bearings versus roller bearings. And as you can imagine, ball bearings have a smaller contact area. They have, you know, theoretically a point contact. So one, a ball resting on a surface makes contact at a point. Now, of course, deformation means it's not perfectly a point, it's more of a circle. Rolling bearings where it's more of a roller, make a line contact, you know, much more of like a rectangular shape when you can account for deformation. And therefore they each have different uses. Rollers can carry higher loads because the contact area is larger. Balls, ball bearings can go at higher speeds because they have a smaller contact area, but then of course, can't carry as high loads. In this portion of the course, we will talk about how you look at the life cycle of a rolling element bearing and how you would go ahead then and select a bearing for a particular application.